Component control in a placement machine

ABSTRACT

Method for component verification during operation of a placement machine having a series of feeder slots for holding component feeders with feeder markers. For verification, whether the right component has been picked up, it is necessary to determine the ID of the actual slot. The method according to the invention determines the actual slot ID from the sequence list of the placement machine.

[0001] The present invention relates to a method for componentverification during operation of a placement machine according to thepreamble of claim 1.

[0002] For electronic board assembly, automated component placement canreach very high speed up to tens of thousands of surface mounts ofcomponents per hour. These components are typically supplied bycomponent vendors as rolled tapes of components that are loaded ontoindividual feeders which are mounted in corresponding feeder slots onthe machine. These rolls of components may be loaded onto the feeders ata special loading unit, for example a stock room, after which the loadedfeeders are placed in the feeder slots.

[0003] Component placement machines can have more than 100 feeder slotseach accessible by a picking mechanism that picks individual componentsfrom the feeders in the slots and places them in particularpredetermined locations on a printed circuit board. For applicationflexibility, each feeder and slot is generally constructed to becompatible with many different components.

[0004] The physical arrangement of components, feeders and slots must bein accordance with the expected arrangement as programmed in themachine. Any error in the arrangement can cause a corresponding error inthe placement of components on the board. In a high volume, low mixmanufacturing environment, a component loading error can produce a highnumber of defective printed circuit boards in a short period of time. Ina low volume, high mix environment the chance of component loading errorincreases because of frequent feeder manipulation for product changeover.

[0005] In order to eliminate loading errors, it is known to place barcode labels on individual feeders and slots for manual scanning tocontrol that the rights components indeed are placed in the right slotsaccording to predetermined configuration information, the so called adevice list, which contains a listing of the slots and the componentsthat are expected in the different slots. This procedure is carried out,before the machine begins its operation.

[0006] A different control system has been disclosed in U.S. Pat. No.6,027,019. In this system, two scanners are adapted to monitor thearrangement of slot markers and feeder markers in the machine while themachine is in operation. The read slot marker and feeder marker are thencompared with data in a device list.

[0007] In known machines, as for example indicated in U.S. Pat. No.6,027,019, slot markers are far away from the corresponding feedermarker, which is due to constructional reasons. Therefore, two scannersare used and not just one single scanner that is able to scan bothmarkers simultaneously.

[0008] In a production environment, those scanners may be exposed todirt that may cover the reading unit resulting in an unsatisfactorycontrol. Furthermore, the scanners are subject to risk of damage duringmachine maintenance or service. Therefore, it may be desirable to reducethe number of necessary scanners. Especially the slot scanner is subjectto this risk in known machines.

[0009] Furthermore, a scanning of both the slot marker and the feedermarker implies that the component has to be picked up always at the sameposition, typically the central position, with respect to the slot.However, for some components, it is an advantage to pick up thecomponent near to the edge of the feeder. This implies no problem forthe feeder scanner, as the feeder marker may be at the pick up positionof the feeder, but the slot reading cannot be performed properly in thiskind of situations. For this reason it may be desirable to avoid theslot marker scanner.

[0010] To avoid installation of a slot marker scanner, a system forcommercially available placement machines has been constructed where adetector counts the number of rotations of a spindle used to displacethe slots in front of the component pick-up. This way, the actual countin the detector is associated with the actual slot. Simultaneously, thefeeder marker is scanned in order to verify that the slot and thecomponent in the feeder of that slot are in accordance with theassociated device list. Such a system is commercially available from thecompany named Surpass Technologies Limited.

[0011] For this kind of counters, regular calibration is necessary,because drift in the mechanical system of the counter may lead tomalfunction. Also, in case of electric failure, the counter needscalibration before being ready to operate. Conventional calibration ofthe control mechanism needs stopping of the operation of the completemachine and translation of the slot table to a position well defined forthe counter. Stopping of the machine, however, is not desirable. Thiskind of system is not well suited for feeders, which have a non-centeredpickup position.

[0012] It is the purpose of the invention to improve control systems forplacement machines, in particular to provide a new system for componentpick-up control where only one scanner, the feeder scanner, isnecessary.

[0013] This purpose is achieved by a method as mentioned by way ofintroduction and characterised according to the characterising part ofclaim 1.

[0014] The method according to the invention relates to a placementmachine, which for example may be used for production of electronicprinted circuit boards as referred to in the following. However, themethod is general and relates to other placement machines equally well.

[0015] It may be noticed for better understanding of the following thatcontrol methods and systems often are applied to already existingplacement machines. From the placement machines, certain data, assequence lists, may be read, but the placement machines generally workindependent of the control systems, which usually are implemented as anadditional tool for the user, for example the operator of the placementmachine.

[0016] In the following the term ID will be used as a short notation foridentification means.

[0017] Such a placement machine has a series of feeder slots, whichtypically are mounted on a platform, for holding component feeders withcorresponding feeder markers. Each feeder marker is associated with acomponent ID, indicative of the type of component contained in thecorresponding feeder; Furthermore, each feeder slot has a slot ID. It isassumed that the placement machine operates in correlation with arepeated sequence list with sequential operating steps.

[0018] During operation of the machine, where the machine is in progressof picking a component from the actual feeder slot, the feeder markerfrom the actual feeder in the actual slot is scanned by an appropriatescanner. Typically such a feeder marker is a bar code, which is scannedby a bar code scanner. The trigger mechanism for the scanner to performthe scanning operation may be a sensor sensing the movement of thepicking mechanism. As the feeder marker is associated to the componentID, scanning the feeder marker verifies the actual component ID. Itshould be pointed out that in the following, for simplification, theterm feeder marker is used as a synonym for the actual feeder marker andthe associated feeder ID that may occur in lists and other softwareapplications.

[0019] In addition, the actual slot ID is determined. From storedconfiguration information, for example a so called device list whichcontains a listing of the slots and the components that are expected inthe different slots, the intended component ID for the componentexpected in the actual slot is extracted.

[0020] The intended component ID refers to the expected component to befound in the actual slot according to stored configuration information,while the actual component ID refers to the component which actually istaken from the actual feeder in the actual slot. These two ID arecompared, and in case of discrepancy between the intended component IDand the actual component ID, the discrepancy is indicated, for exampleby an alert to the operator of the machine.

[0021] The method according to the invention differs from prior art inthe determination of the actual slot, which is explained in thefollowing. It is known that the placement machine operates in accordanceto a sequence list with sequential steps, where the sequence list isrepeated from the beginning of the list each time the production of anew product, for example a printed circuit board, is begun, Therefore,while the placement machine is operating, the sequential step number ofthe actual step of operation of the placement machine may be determined.This can, for example, be achieved by reading a start signal, when asequence starts, and counting the number of operational steps of theplacement machine.

[0022] Having determined the sequential step, the slot ID is determinedfrom the sequence list, as sequential step in this list is linked to theactual slot ID. Thus, the slot ID may be determined even without aposition detector or a slot scanner, which is a new approach allowing tocontrol a placement machine in a much simpler way. In addition, thesystem is also easy to implement in already existing placement machines.Furthermore, a system without a position detector or a slot scanner ismuch cheaper and does not suffer from the need of steady calibration orfrom a malfunctioning slot scanner, making the system also more safe. Italso allows the use of feeders, which have a non centered pickupposition.

[0023] The start signal to be read in the beginning of a new sequencemay be achieved from the placement machine directly or by other means,for example from an appropriate sensor.

[0024] The counting of the steps from the beginning of the sequence listis possible, for example by reading of a trigger signal for each step.This trigger signal can, for example, be based on the movement of thepicking mechanism.

[0025] In most cases, the above described counting of the steps andfollowed determining of the actual slot according to the sequence listworks perfectly. However, in some cases, difficulties may arise, whichis explained in the following. Some placement machines take into accountthat a component after pick up may be lost. In this case, a renewed pickup of the intended component may not be possible before the nextcomponent is picked up. The missed component may then be picked up at alater time which causes a deviation from the original sequence list andmay lead to a false determination of the actual slot from the sequencelist.

[0026] In a further embodiment of the invention, a solution has beenfound for this situation which is explained in the following. For thisreason, an association is created between each actual feeder marker andthe corresponding actual slot ID. For simplicity this association willbe called a connection list, which is synonym for such a list and anyother type of software association. Such a list is configured at eachstart of a sequence. Upon receipt of a pick up trigger signal for asequential step, a control is performed, whether the actual feedermarker is already contained in this connection list.

[0027] If this is not the case, the feeder marker and associated slotID, determined from the sequence list, is added to the connection list.This way, the connection list is updated for each sequential step. Ithas to be pointed out that in this case, the pick up cannot be a renewedpick up, because a renewed pick up would have implied access to thecorresponding feeder at an earlier stage, which would result in thefeeder marker having been added to the connection list already.

[0028] If the actual feeder marker on the other hand is found in theconnection list, the corresponding slot ID from the connection list iscompared with the actual slot ID as determined from the sequence listand, in case of disagreement, the actual pick up must be a renewed pickup. In this case, the counting of said trigger signal is avoided,because the step according to the sequence list has not yet beenperformed. For documentation reasons, an indication for such a renewedpick up may be stored together with time data and other data, forexample the product serial number.

[0029] The method as described above may typically involve a computerfor the control procedures and calculations and works without a slotposition detector that indicates by position readings which actual slota component is taken from. Avoiding such a detector cures some of themistakes that may occur in the production process of placement machines.However, on the other hand, some other mistakes may occur, if the methodas described above is used without a position detector. In other words,using a position detector to find the actual slot ID avoids somemistakes on a whole, while the method according to the invention mayavoid other mistakes in the production process. In order to minimise thenumber of possible mistakes, a combination of a position detector andthe above described method according to the invention is foreseen by theinvention in the following still further embodiment.

[0030] According to this still further embodiment of the invention, itis assumed that a slot position detector is employed, from whichdetector signal is read, the detector signal being indicative of theposition of the actual slot. Furthermore in accordance with suchreadings, an association is stored between each slot ID and acorresponding detector signal. For simplicity, this association will becalled a position list being a synonym for such a list and any otherform of this association. For each pick up, the detector signal is readand checked, whether said reading corresponds to a specific slot ID. Ifthis is the case, the actual slot ID is determined from this reading,which is a conventional way for determining the actual slot ID. As thedetector may be subject to drift, the reading value may be slightlydifferent from earlier readings. This is foreseen in the invention, asthe reading is accepted as being associated with a specific slot ID, ifthe read value is within a predetermined uncertainty interval. Thisinterval is set large enough to accept slight drift of the detector, butsmall enough to assure, that the detector reading can be associated witha slot ID. However, if the value is outside this predetermineduncertainty interval, the slot ID may not be determined with certaintyfrom the detector reading. In this case, the actual slot ID isdetermined from the sequence list with the method as described above andwill be associated with the detector signal. Furthermore, the positionlist is edited correspondingly to contain the new association.

[0031] A problem may also occur if the position detector has beensubject to a power failure. In this case, the reading of the detectormay change for a specific slot such that the reading cannot be found inthe position list. In this case, an initial calibration has to beperformed. According to the invention, this problem has been foreseenand is cured by determining the actual slot ID from the sequence list bythe method as described above after which the reading of the detector isassociated with the determined actual slot in a new position list.

[0032] The association between a feeder marker and a specific componentID is achieved by scanning a specific feeder label of a specific feederand scanning a component label indicative of the specific component typeto be loaded into said specific feeder prior to installation of saidspecific feeder in the placement machine.

[0033] The invention may be used for printed electronic circuit boardsbut applies equally to any other product produced in such type ofmachine.

[0034] The invention will be explained in more detail in the followingwith reference to the drawings, where

[0035]FIG. 1 is a diagram of a placement machine,

[0036]FIG. 2 is a diagram showing the principles for component control,

[0037]FIG. 3 is a diagram showing the principles for determining theslot ID according to the invention,

[0038]FIG. 4 is a diagram showing the principles for component controltaking into account renewed pick ups,

[0039]FIG. 5 is a diagram configuration of the position list,

[0040]FIG. 6 is a diagram showing the principle for calibration of theposition detector.

[0041] In FIG. 1, a placement machine 101 is illustrated having aplatform 102, on which a number of slots 103 are located. Into each slot103, a feeder 104 may be placed. Certain feeder 104 types may extendinto several slots 103. The platform 102 is displaced relatively to thecomponent pick up arm 105 for picking up components from different slots103. Alternatively, the pick up arm 105 may be displaced with respect tothe platform 102.

[0042] Each feeder 104 is provided with an identification marker, forexample a bar code label, which is readable by an appropriate scanner109. When the platform 102 is placed at a particular position to pick upa component from a specific slot 103, the feeder marker of the feeder104 in the specific slot 103 is read and the reading transferred to thecomputer 108. The reading of the feeder marker is initiated by a pick uptrigger signal, which may be due to a signal by a sensor 110, whichsenses the movement of the pick up arm 105 of the placement machine 101.

[0043] Normally, when component reels are loaded into a feeder 104, thefeeder marker is read and stored together with the component ID of thecomponent reel. Thus, the feeder marker of the actual feeder 104 in theactual slot 103, from which a component is to be taken, is associated tothe component ID. The computer is configured to have access to thesedata, which is illustrated in FIG. 2 as a feeder/component list 201.Therefore, scanning 202 the feeder marker, which implicit is associatedwith a feeder ID 203, reveals the actual component type 204′. Scanningof the feeder marker is initiated by a pick up trigger signal 205 asdescribed above. In connection with the same pick up, the actual slot ID208 is determined by a routine operation 206. From stored configurationinformation, shown as device list 207, the intended component ID 204 ofthe type of component expected in this determined slot with actual slotID 208 may be found. The control system aims for checking 209, whetherthe intended component 204 and the actual component 204′ are identical.If a wrong actual component 204′ has been picked up, this is indicatedfor example by an alert 210 to the operator.

[0044] In FIG. 3, an embodiment is shown for the routine operation 206to determine the actual slot ID. When the placement machine starts theproduction of a new product, the sequence list is at the beginning and asequence start signal 301 is read. In order to count the number ofsequential steps, a step counter routine 302 may be employed with acounting mechanism. As a response to the start signal 301, the counteris reset 303 to the step value 1. At the receipt of each trigger pick upsignal 205, the step count is read 304 and advanced 305 one step. Fromthe sequence list 306 the actual slot ID 208 corresponding to the actualstep 308 is determined, which then, as shown in FIG. 2, is used todetermine the intended component type 204 from the device list 207.

[0045] This method can thus be used to determine the actual slot ID 208without the need of a position detector. However, in case that theplacement machine 101 looses a component after pick up and then performsa renewed pick up at a later stage, this method does not functionproperly.

[0046] The problem with renewed pick ups is solved by the alternativeembodiment of the routine 206 as illustrated in the diagram of FIG. 4and explained in the following. This embodiment employs a step counter302 in the same way as just mentioned and a connection list 401, where afeeder ID 203 is associated with a corresponding slot ID 407 asdetermined.

[0047] At a response to the start signal 301, the step counter is reset303 and the connection list 401 is cleared 402. For each trigger signal205, the scanner is read 202, and a routine 403 checks, whether, thescanned feeder marker with associated feeder ID 203 can be found in theconnection list 401.

[0048] If this is not the case 412, the step number is read 304 andadvanced 305. From the sequence list 306 the actual slot 307corresponding to the step 308 is determined. The new feeder/slotcombination is added 404 to the connection list 401, and the actual slot307 is used as the result for the determined slot ID 208 to be used tofind the intended component 204 from the device list 207 as illustratedin FIG. 2.

[0049] If the feeder ID associated with the scanned feeder marker on theother hand is in the connection list 413, the corresponding slot ID 407from the connection list 401 is compared by a routine 405 with theactual slot ID 307 as found from the sequence list 306. If these two ID307, 407 are identical 408, a type of component has been picked up whichis equal to a type of component that has been picked up at an earlierstage. The feeder/slot combination is already stored in the connectionlist, which therefore need not be edited. For the next sequential step,the step counter 302 is advanced 305 one step. However, if these twoslot ID 307, 407 are not identical 409, the pick up has been a renewedpick up 410 of an earlier lost component. In this case, the counter 302is not advanced. The actual slot ID 208 to be used in connection withthe component control as illustrated in FIG. 2 is determined from theconnection list 401, as the reading 202 of the feeder marker withassociated feeder ID 203 results in the actual slot ID 407 from theconnection list 401.

[0050] In case that a feeder 104 runs out of components, the placementmachine 101 may stop automatically. The feeder 104 will then typicallybe changed with another feeder at hand containing this type ofcomponent. After this exchange, which may be done by the operator, thefeeder/slot combination may be different than stored in the connectionlist, because it is possible to move feeders, when the machine isstopped. Therefore, each time the production with the placement machine101 is stopped, and a corresponding stop signal is received 411, theconnection list 401 is cleared 402.

[0051] The method as described may typically involve a computer for thecontrol procedures and calculations and works without a slot positiondetector. However, some mistakes may occur, if the method as describedabove is used without a position detector. Therefore, a combination of aposition detector and the above described method according to theinvention is preferred.

[0052] An example of when the method according to the invention resultsin malfunction is given in the following. If a feeder 104 runs out ofcomponents, the placement machine 101 is stopped and the feeder 104 maybe changed with a new feeder holding the same component type. In thiscase for above reasons, the connection list 401 is cleared. That meanshowever that a renewed pick up during the remaining sequence is notdetected and results in an alarm 210 to the operator, as illustrated inFIG. 2, because the determined slot ID 307 from the sequence list 306,as shown in the upper part of FIG. 4, leads to an intended component ID204, as illustrated n FIG. 2, which is different from the renewed pickup component 204′.

[0053] This situation is rare, but is one of the faults that may occurand delay the production process with increased production cost as aresult. In order to avoid these type of faults, a related error messagemay be received from the placement machine 101 and used in connectionwith the invention to take into account this type of pick up. Howevernot always, placement machines 101 may make such an error messageavailable.

[0054] Also, the operator may choose to skip this component and placethe mount of the component in another stage in the production process.In these cases, the above described embodiments of the invention do notwork properly. Therefore, it is foreseen in this invention that aposition detector may be employed in addition to the method according tothe invention.

[0055] It may be questioned, whether the method according to theinvention is useful if a detector is used anyhow. However, the methodaccording to the invention is necessary, for example if theidentification of the actual slot by the detector does not functionproperly, which may be the case when the detector has been subject to apower failure, when the position detector changes its reading due tocalibration drift, or when a feeder with an off-centered pickup positionis used.

[0056] In the following, it is assumed, that a position detector isemployed in connection with the control system of the placement machine,for example as illustrated in FIG. 1. The platform 102 is displacedlinearly along a spindle 106 due to rotation of the spindle. A detector107 with an encoder translates the rotation of the spindle 106 into dataindicative of a longitudinal position of the platform 102 relative to areference point. In the detector 107 or in the connected computer 108,for example a personal computer, the position may be calculated fromthese data.

[0057] In this case, the slot ID 208 may be determined as illustrated inFIG. 5. As a response to a pick up trigger signal 205, the encoder valueis read 501. Usually, this value is offset from a reference position,which is illustrated by the reference value 502, which is stored forcalculation 503 of the position. For each slot 103, the signal, valE,from the encoder is read and the position 504, or any data indicative ofthe position, for each slot is stored in the position list 505 inassociation with the corresponding slot ID 510.

[0058] The detector 107 may be initialised by an initialising signal 506in order to set the reference value 507. Also, in response to acalibration signal 508, the position list 505 may be updated 509.

[0059] Once this position list 505 has been established, it may be usedto extract the slot ID 510 corresponding to the position 504 as readfrom the detector 107 and the determined slot ID 510 from the positionlist is used as the slot ID 208 for the component verification procedureas illustrated in FIG. 2.

[0060] As the detector 107 may be subject to drift, the reading valuemay be slightly different from earlier readings. This is foreseen in theinvention in a procedure 511, as the position 504 reading is accepted asbeing a good reading and associated with a specific slot ID 510, if theread value is within a predetermined uncertainty interval. This intervalis set large enough to accept slight drift of the detector 107, butsmall enough to assure, that the detector reading can be associated witha slot ID. If the read value differs slightly from earlier readings butare still within the acceptable limits of the predetermined uncertaintyinterval, the position list is updated in a calibration procedure 508.The determination of the slot ID 208 as illustrated in FIG. 5 isillustrated in FIG. 6 as procedure 601.

[0061] However, if the position value is outside this predetermineduncertainty interval, the slot ID may not be determined with certaintyfrom the detector reading and the reading is deemed a bad reading 512 asillustrated in FIG. 5. As a consequence of this bad reading 512, whichis checked for in routine 602, the actual slot ID 208 to be used for thecomponent verification as illustrated in FIG. 2 is determined 604 fromthe sequence list 306 with the method as described above and illustratedin FIG. 4. The determined slot ID 208 in this case is used for acalibration 508 of the detector 107

[0062] A problem may also occur, if the position detector 107 has beensubject to a power failure. In this case, the reading of the detector107 may change for a specific slot 103 such that the reading cannot befound in the position list 505. Therefore after receipt of each triggersignal 205, it is checked 605, whether the position detector 107 hasjust been powered up after the power failure. In this case, an initialcalibration 506 has to be performed. According to the invention, thisproblem has been foreseen and is cured by determining the actual slot ID208 from the sequence list by the method 604 as described above andillustrated in FIG. 4. In the initialisation process 506 the referenceposition reading is associated with the determined actual slot ID 208which constitutes a basis for the configuration of the referenceposition 507.

[0063] As explained above, the invention may be applied in controlsystems for placement machines without the use of a position detectorwhich may be an advantage in case that a minimum of hardware ispreferred. On the other hand, the invention may be applied in connectionwith a position detector, where the invention takes into accountmalfunction of a detector and therefore minimises the risk forproduction errors.

[0064] List of Numbers

[0065]101: Placement machine

[0066]102: Feeder table, platform to place feeders on

[0067]103: Slot, a feeder fits into a slot

[0068]104: Feeder, contains components

[0069]105: Pickup arm, picks components from feeder

[0070]106: Spindle, moves 102 the feeder table

[0071]107: Detector, detects the rotation of 106 the spindle

[0072]108: Computer

[0073]109: Scanner

[0074]110: Sensor, senses movement of 105 the pickup arm

[0075]201: Feeder and component connection, made when loading feederwith component

[0076]202: Scanning the Feeder ID 203 by the scanner 109

[0077]203: Feeder ID

[0078]204: Component Type

[0079]205: Pick-up signal from the sensor 110

[0080]206: Routine to determine slot, embodiments of this is describedin FIGS. 3, 4, 5 and 6.

[0081]207: Device list, material list from the placement program

[0082]208: Slot ID

[0083]209: Are the intended component ID identical to actual componentID?

[0084]210: Alarm, notify the operator that action must be taken

[0085]301: Start production signal/message

[0086]302: Step, keeps track of the current step in the sequence list

[0087]303: Reset Step to 1, which is the first step in 306 the sequencelist

[0088]304: Read the value of Step

[0089]305: Increase Step

[0090]306: Sequence list

[0091]307: Slot ID in sequence list

[0092]308: Step in sequence list

[0093]401: Connection list between used feeders and the correspondingslot

[0094]402: Clear list, initial no feeders have been used and the list isempty

[0095]403: Is the scanned feeder ID already in the connection list?

[0096]404: Append (Feeder ID, Slot) to the connection list 401

[0097]405: Is slot from sequence list identical to slot from connectionlist?

[0098]407: Slot ID in connection list, will be used as Slot ID in 208

[0099]408: Yes

[0100]409: No

[0101]410: Re-pickup occurred, no actions required

[0102]411: Stop production message/signal, occurs when machineerror-stops during production

[0103]412: No

[0104]413: Yes

[0105]501: Read the encoder value: valE

[0106]502: Reference, to offset the encoder values to positions

[0107]503: Calculate position. Position:=valE−Reference

[0108]504: Position in the position list 505

[0109]505: The position list, which contains the position for each slot.The position list connects the readings from the encoder with the actualslot ID's

[0110]506: Initialise signal/message to calculate the reference value

[0111]507: Calculate Reference

[0112]508: Calibrate signal/message to calibrate a position

[0113]509: Calculate position in 505 position list

[0114]510: Slot ID in position list

[0115]511: Is the reading of the encoder within acceptable limits todetermine a slot?

[0116]512: The reading of the encoder is useless (not within acceptablelimits)

[0117]601: Find the Slot ID as described in FIG. 5 (using an encoder)

[0118]602: Was it not possible to determine the slot from the encodervalue?

[0119]603: Yes, the encoder value did not correspond to a slot position.On FIG. 5 this would result in 512 Bad Reading, else the slot 208 wouldbe determined.

[0120]604: Find the Slot ID as described in FIG. 4 (using the sequencelist)

[0121]605: Is the encoder just powered up after a power cut?

1. Method for component verification during operation of a placementmachine (101) having a series of feeder slots (103) for holdingcomponent feeders (104) with feeder markers, each feeder markerassociated with a component ID (204′) indicative of the type ofcomponent contained in the corresponding feeder (203), wherein eachfeeder slot (103) has a slot ID (208), wherein said placement machineoperates in correlation with a repeated sequence list (306) withsequential steps, said method comprising upon receipt of a pick uptrigger signal (205) scanning a feeder marker from the actual feeder(104) in said actual feeder slot (103), while the machine (101) is inprogress of picking a component from said actual feeder (104), todetermine the actual component ID (204′) associated with the feedermarker, determining (206) the actual slot ID (208), determining fromstored configuration information (207) the intended component ID (204),where the intended component ID (204) is the ID of the type of componentintended to be picked up from said actual feeder slot (104), comparingsaid intended component ID (204) with said actual component ID (204′),in case of discrepancy between said intended component ID (204) and saidactual component ID (204′) indicating said discrepancy, whereindetermining (206) said actual slot ID (208) comprises determining thesequential step number of the actual step (308) and reading from saidsequence list (306) the associated actual slot ID (208).
 2. Methodaccording to claim 1, wherein said determining said sequential numbercomprises, at the start of a sequence, reading a sequence start signal(301) and counting said pick up trigger signals (305).
 3. Methodaccording to claim 1 wherein said pick up trigger signal (205) comprisesa signal from a sensor (110) sensing the movement of the pickingmechanism of the placement machine (101).
 4. Method according claim 2,wherein to any single claim of said method further comprises configuringa connection list (401) for associating the actual feeder marker (203)with the determined actual slot ID (407), upon receipt of said pick uptrigger signal checking whether said actual feeder marker (203) iscontained in said connection list (401) if this is not the case, addingsaid feeder marker (203) and associated determined slot ID (407) to saidconnection list, if this is the case, comparing the corresponding slotID (407) from the connection list with the actual slot ID (307) asdetermined from the sequence list (306), and in case of disagreement,avoiding (410) of said counting (305) of said trigger signal (205). 5.Method according to claim 4, wherein said avoiding (410) of saidcounting said trigger signal (205) further implies storing an indicationfor a renewed pick up.
 6. Method according to claim 5, wherein saidmethod involves reading (501) of a detector signal (504) from a slotposition detector (107), configuring a position list (505) forassociating a detector signal (504) with each slot ID (510), checking(511) for each further reading of a detector signal (504) whether saidreading within a predetermined uncertainty interval is contained in saidposition list (505), and if this is not the case (603), editing (508)said position list (505) and associating (508) said detector signal(504) with said determined (604) slot ID (208) from said sequence list(306).
 7. Method according to claim 1, wherein said method involvesreading (501) of an actual detector signal from a slot position detector(107), and in case that said slot position detector (107) has juststarted operation after a power failure (605) associating said actualdetector signal with said determined (604) actual slot ID (208). 8.Method according claim 1, wherein said step of indicating saiddiscrepancy comprises alerting (210) an operator.
 9. Method accordingclaim 1, wherein said association (201) between a feeder marker (203)and a specific component ID (204′) is achieved by scanning a specificfeeder marker (203) of a specific feeder (104) and scanning a componentlabel indicative of the specific component type (204′) to be loaded intosaid specific feeder (104) prior to installation of said specific feeder(104) in the placement machine (101).
 10. Method of controlling aplacement machine (101) for production of printed electronic circuits,having a series of feeder slots (103) for holding component feeders(104) with feeder markers, each feeder marker associated with acomponent ID (204′) indicative of the type of component contained in thecorresponding feeder (203), wherein each feeder slot (103) has a slot ID(208), wherein said placement machine operates in correlation with arepeated sequence list (306) with sequential steps, comprising the stepsof: upon receipt of a pick up trigger signal (205), scanning a feedermarker from the actual feeder (104) in said actual feeder slot (103),while the machine (101) is in progress of picking a printed electroniccircuit from said actual feeder (104), to determine the actual componentID (204′) associated with the feeder marker, determining (206) theactual slot ID (208), determining from stored configuration information(207) the intended component ID (204), where the intended component ID(204) is the ID of the type of component intended to be picked up fromsaid actual feeder slot (104), comparing said intended component ID(204) with said actual component ID (204′), in case of discrepancybetween said intended component ID (204) and said actual component ID(204′) indicating said discrepancy, wherein determining (206) saidactual slot ID (208) comprises determining the sequential step number ofthe actual step (308) and reading from said sequence list (306) theassociated actual slot ID
 11. Method for component verification duringoperation of a placement machine (101) having a series of feeder slots(103) for holding component feeders (104) with feeder markers, eachfeeder marker associated with a component ID (204′) indicative of thetype of component contained in the corresponding feeder (203), whereineach feeder slot (103) has a slot ID (208), wherein said placementmachine operates in correlation with a repeated sequence list (306) withsequential steps, said method comprising upon receipt of a pick uptrigger signal (205) scanning a feeder marker from the actual feeder(104) in said actual feeder slot (103), while the machine (101) is inprogress of picking a component from said actual feeder (104), todetermine the actual component ID (204′) associated with the feedermarker, determining (206) the actual slot ID (208), determining fromstored configuration information (207) the intended component ID (204),where the intended component ID (204) is the ID of the type of componentintended to be picked up from said actual feeder slot (104), comparingsaid intended component ID (204) with said actual component ID (204′),in case of discrepancy between said intended component ID (204) and saidactual component ID (204′) indicating said discrepancy, wherein thedetermining (206) of said actual slot ID (208) comprises: determiningthe sequential step number of the actual step (308) and reading fromsaid sequence list (306) the associated actual slot ID (208).configuring a connection list (401) for associating the actual feedermarker (203) with the determined actual slot ID (407), upon receipt ofsaid pick up trigger signal checking whether said actual feeder marker(203) is contained in said connection list (401) if this is not thecase, adding said feeder marker (203) and associated determined slot ID(407) to said connection list, if this is the case, comparing thecorresponding slot ID (407) from the connection list with the actualslot ID (307) as determined from the sequence list (306), and in case ofdisagreement, avoiding (410) of said counting (305) of said triggersignal (205).
 12. Method according to claim 11, wherein said determiningsaid sequential number comprises at the start of a sequence reading asequence start signal (301) and counting said pick up trigger signals(305).
 13. Method according to claim 11, wherein said pick up triggersignal (205) comprises a signal from a sensor (110) sensing the movementof the picking mechanism of the placement machine (101).
 14. Methodaccording to claim 11, wherein said avoiding (410) of said counting saidtrigger signal (205) further implies storing an indication for a renewedpick up.
 15. Method according to claim 11, wherein said method involvesreading (501) of a detector signal (504) from a slot position detector(107), configuring a position list (505) for associating a detectorsignal (504) with each slot ID (510), checking (511) for each furtherreading of a detector signal (504) whether said reading within apredetermined uncertainty interval is contained in said position list(505), and if this is not the case (603), editing (508) said positionlist (505) and associating (508) said detector signal (504) with saiddetermined (604) slot ID (208) from said sequence list (306).
 16. Methodaccording to claim 11, wherein said method involves reading (501) of anactual detector signal from a slot position detector (107), and in casethat said slot position detector (107) has just started operation aftera power failure (605) associating said actual detector signal with saiddetermined (604) actual slot ID (208).
 17. Method according to claim 11,wherein said association (201) between a feeder marker (203) and aspecific component ID (204′) is achieved by scanning a specific feedermarker (203) of a specific feeder (104) and scanning a component labelindicative of the specific component type (204′) to be loaded into saidspecific feeder (104) prior to installation of said specific feeder(104) in the placement machine (101).
 18. Method for componentverification during operation of a placement machine (101) having aseries of feeder slots (103) for holding component feeders (104) withfeeder markers, each feeder marker associated with a component ID (204′)indicative of the type of component contained in the correspondingfeeder (203), wherein each feeder slot (103) has a slot ID (208),wherein said placement machine operates in correlation with a repeatedsequence list (306) with sequential steps, said method comprising uponreceipt of a pick up trigger signal (205) scanning a feeder marker fromthe actual feeder (104) in said actual feeder slot (103), while themachine (101) is in progress of picking a component from said actualfeeder (104), to determine the actual component ID (204′) associatedwith the feeder marker, determining (206) the actual slot ID (208),determining from stored configuration information (207) the intendedcomponent ID (204), where the intended component ID (204) is the ID ofthe type of component intended to be picked up from said actual feederslot (104), comparing said intended component ID (204) with said actualcomponent ID (204′), in case of discrepancy between said intendedcomponent ID (204) and said actual component ID (204′) indicating saiddiscrepancy, wherein the determining (206) of said actual slot ID (208)comprises: determining the sequential step number of the actual step(308) and reading from said sequence list (306) the associated actualslot ID (208), reading (501) of a detector signal (504) from a slotposition detector (107), configuring a position list (505) forassociating a detector signal (504) with each slot ID (510), checking(511) for each further reading of a detector signal (504) whether saidreading within a predetermined uncertainty interval is contained in saidposition list (505), and if this is not the case (603), editing (508)said position list (505) and associating (508) said detector signal(504) with said determined (604) slot ID (208) from said sequence list(306).
 19. Method according to claim 18, wherein said determining saidsequential number comprises at the start of a sequence reading asequence start signal (301) and counting said pick up trigger signals(305).
 20. Method according to claim 18, wherein said pick up triggersignal (205) comprises a signal from a sensor (110) sensing the movementof the picking mechanism of the placement machine (101).
 21. Methodaccording to claim 18, wherein said method involves reading (501) of anactual detector signal from a slot position detector (107), and in casethat said slot position detector (107) has just started operation aftera power failure (605) associating said actual detector signal with saiddetermined (604) actual slot ID (208).
 22. Method according to claim 19,wherein said association (201) between a feeder marker (203) and aspecific component ID (204′) is achieved by scanning a specific feedermarker (203) of a specific feeder (104) and scanning a component labelindicative of the specific component type (204′) to be loaded into saidspecific feeder (104) prior to installation of said specific feeder(104) in the placement machine (101).